OF THE

EXTERNAL SENSES.

THE

HE Senfes, by which we perceive external objects, are commonly reckoned Five in Number; Seeing, Hearing, Smelling, Tafting, and Touching.

Of thefe, the four first mentioned are each of them confined to particular parts or organs of the body; the Senfe of Seeing is confined to the Eyes; that of Hearing to the Ears; that of Smelling to the Noftrils; and that of Tafting to the Palate. The Senfe of Touching alone feems not to be confined to any particular organ, but to be diffused through almost every part of the body; if we except the hair and the nails of the fingers and toes, I believe through every part of it. I fhall fay a few words concerning each of these Senses; beginning with the laft, proceeding backwards in the oppofite order to that in which they are commonly enumerated.

Of the Senfe of TOUCHING.

THE objects of Touch always prefent themfelves as preffing upon, or as refifting the particular

ticular part of the body which perceives them, or by which we perceive them. When I lay my hand upon the table, the table preffes upon my hand, or refifts the further motion of my hand, in the fame manner as my hand preffes upon the table. But preffure or refistance neceffarily fuppofes externality in the thing which preffes or refifts. The table could not prefs upon, or refift the further motion of my hand, if it was not external to my hand. I feel it accordingly, as fomething which is not merely an affection of my hand, but altogether external to and independent of my hand. The agreeable, indifferent, or painful fenfation of preffure, according as I happen to prefs hardly or foftly, I feel, no doubt, as affections of my hand; but the thing which preffes and refifts I feel as fomething altogether different from thofe affections, as external to my hand, and as altogether independent of it.

In moving my hand along the table it foon comes, in every direction, to a place where this preffure or refiftance ceafes. This place we call the boundary, or end of the table; of which the extent and figure are determined by the extent and direction of the lines or furfaces which conftitute this boundary or end.

It is in this manner that a man born blind, or who has loft his fight fo early that he has

no remembrance of vifible objects, may form the most distinct idea of the extent and figure of all the different parts of his own body, and of every other tangible object which he has an opportunity of handling and examining. When he lays his hand upon his foot, as his hand feels the preffure or refiftance of his foot, fo his foot feels that of his hand. They are both external to one another, but they are, neither of them, altogether fo external to him. He feels in both, and he naturally confiders them as parts of himself, or at least as fomething which belongs to him, and which, for his own happiness and comfort, it is neceffary that he should take fome care of.

When he lays his hand upon the table, though his hand feels the preffure of the table, the table does not feel, at least he does not know that it feels, the preffure of his hand. He feels it therefore as fomething external, not only to his hand, but to himself, as something which makes no part of himself, and in the state and condition of which he has not neceffarily any concern.

When he lays his hand upon the body either of another man, or of any other animal, though he knows, or at least may know, that they feel the preffure of his hand as much as he feels that of their body: yet as this feeling is altogether external to him, he frequently gives no attention to it, and at no time takes

any

any further concern in it than he is obliged to do by that fellow-feeling which Nature has, for the wifeft purposes, implanted in man, not only towards all other men, but (though no doubt in a much weaker degree) towards all other animals. Having destined him to be the governing animal in this little world, it feems to have been her benevolent intention to infpire him with fome degree of refpect, even for the meanest and weakest of his fubjects.

This power or quality of refiftance we call Solidity; and the thing which poffeffes it, the Solid Body or Thing. As we feel it as fomething altogether external to us, fo we necef farily conceive it as fomething altogether independent of us. We confider it, therefore, as what we call a Subftance, or as a thing that fubfifts by itself, and independent of any other thing. Solid and fubftantial, accordingly, are two words which, in common language, are confidered either as altogether, or as nearly fynonimous.

Solidity neceffarily fuppofes fome degree of extenfion, and that in all the three directions of length, breadth, and thickness. All the folid bodies, of which we have any experi ence, have fome degree of fuch bulk or magnitude. It feems to be effential to their nature, and without it, we cannot even con-. ceive how they should be capable of preffure

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or refiftance; the powers by which they are made known to us, and by which alone they are capable of acting upon our own, and upon all other bodies.

Extenfion, at least any fenfible extenfion, fuppofes divifibility. The body may be fo hard, that our ftrength is not fufficient to break it: we still fuppofe, however, that if a fufficient force were applied, it might be fo broken; and, at any rate, we can always, in fancy at least, imagine it to be divided into two or more parts.

Every folid and extended body, if it be not infinite, (as the universe may be conceived to be,) must have fome fhape or figure, or be bounded by certain lines and furfaces.

Every fuch body muft likewise be conceived as capable both of motion and of reft; both of altering its fituation with regard to other furrounding bodies, and of remaining in the fame fituation. That bodies of fmall or moderate bulk, are capable of both motion and reft we have conftant experience. Great maffes, perhaps, are, acccording to the ordinary habits of the imagination, fuppofed to be more fitted for reft than for motion. Provided a fufficient force could be applied, however, we have no difficulty in conceiving that the greatest and most unwieldy maffes might be made capable of motion. Philofo

VOL. V.

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phy